RESUMEN
In the present study, the expression of somatostatin (SST) and somatostatin receptor subtypes (SSTR1-5) was determined in the hypothalamus of wild-type (wt) and apolipoprotein D knockout (ApoD(-/-)) mice brain. SST-like immunoreactivity, while comparable in most regions of hypothalamus, diminished significantly in arcuate nucleus of ApoD(-/-) mice. SSTR1 strongly localized in all major hypothalamic nuclei as well as in the median eminence and ependyma of the third ventricle of wt mice brain. SSTR1-like immunoreactivity increases in hypothalamus except in paraventricular nucleus of ApoD(-/-) mice. SSTR2 was well expressed in most of the hypothalamic regions whereas it decreases significantly in ventromedial and arcuate nucleus of ApoD(-/-) mice. SSTR3 and SSTR4-like immunoreactivity increases in ApoD(-/-) mice in all major nuclei of hypothalamus, median eminence, and ependymal cells of third ventricle. SSTR5 is well expressed in ventromedial and arcuate nucleus whereas weakly expressed in paraventricular nucleus. In comparison to wt, ApoD(-/-) mice exhibit increased SSTR5-like immunoreactivity in paraventricular nuclei and decreased receptor expression in ventromedial hypothalamus and arcuate nucleus. In conclusion, the changes in hypothalamus of ApoD(-/-) mice may indicate potential role of ApoD in regulation of endocrine functions of somatostatin in a receptor-dependent manner.
Asunto(s)
Apolipoproteínas D/deficiencia , Hipotálamo/química , Receptores de Somatostatina/análisis , Somatostatina/análisis , Animales , Apolipoproteínas D/genética , Western Blotting , Ventrículos Cerebrales/química , Epéndimo/química , Hipotálamo/ultraestructura , Técnicas para Inmunoenzimas , Eminencia Media/química , Ratones , Ratones Noqueados , Especificidad de Órganos , Receptores de Somatostatina/clasificación , Receptores de Somatostatina/fisiología , Somatostatina/fisiologíaRESUMEN
Metabolic interaction via lactate between glial cells and neurons has been proposed as one of the mechanisms involved in hypothalamic glucosensing. We have postulated that hypothalamic glial cells, also known as tanycytes, produce lactate by glycolytic metabolism of glucose. Transfer of lactate to neighboring neurons stimulates ATP synthesis and thus contributes to their activation. Because destruction of third ventricle (III-V) tanycytes is sufficient to alter blood glucose levels and food intake in rats, it is hypothesized that tanycytes are involved in the hypothalamic glucose sensing mechanism. Here, we demonstrate the presence and function of monocarboxylate transporters (MCTs) in tanycytes. Specifically, MCT1 and MCT4 expression as well as their distribution were analyzed in Sprague Dawley rat brain, and we demonstrate that both transporters are expressed in tanycytes. Using primary tanycyte cultures, kinetic analyses and sensitivity to inhibitors were undertaken to confirm that MCT1 and MCT4 were functional for lactate influx. Additionally, physiological concentrations of glucose induced lactate efflux in cultured tanycytes, which was inhibited by classical MCT inhibitors. Because the expression of both MCT1 and MCT4 has been linked to lactate efflux, we propose that tanycytes participate in glucose sensing based on a metabolic interaction with neurons of the arcuate nucleus, which are stimulated by lactate released from MCT1 and MCT4-expressing tanycytes.
Asunto(s)
Epéndimo/metabolismo , Glucosa/metabolismo , Lactatos/metabolismo , Transportadores de Ácidos Monocarboxílicos/análisis , Proteínas Musculares/análisis , Neuroglía/metabolismo , Neuronas/metabolismo , Simportadores/análisis , Animales , Células Cultivadas , Epéndimo/química , Epéndimo/citología , Hipotálamo/química , Hipotálamo/citología , Metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
Selenoprotein P (SePP) is central to selenium (Se) metabolism in the mammalian organism. Human SePP contains 10 Se atoms that are covalent constituents of the polypeptide chain incorporated as the rare amino acid selenocysteine (Sec). Since hepatocytes secrete SePP into plasma, SePP is commonly regarded as a Se transport protein, although SePP mRNA is expressed in many organs. Gene targeting of SePP in mice leads to neurological dysfunction resulting from Se deficiency and associated reduction of selenoenzyme activities in the brain. However, more recent data revealed that isolated hepatic SePP deficiency does not alter brain Se levels, suggesting a role for SePP locally expressed in the brain. Some of the best characterized and most abundant selenoenzymes, glutathione peroxidases, thioredoxin reductases, and methionine sulfoxide reductase B, play major roles in the cellular defense against reactive oxygen species. Therefore, it was hypothesized that reduced brain Se bioavailability may be involved in the pathogenesis of neurodegenerative disease and normal ageing. We present evidence that human CSF contains SePP and that the human brain expresses SePP mRNA. Moreover, SePP-like immunoreactivity localizes to neurons and ependymal cells and thus appears strategically situated for maintenance and control of Se-dependent anti-oxidative defense systems.
Asunto(s)
Encéfalo/metabolismo , Epéndimo/metabolismo , Regulación de la Expresión Génica , Neuronas/metabolismo , Proteoma/biosíntesis , Selenoproteína P/biosíntesis , Selenoproteína P/metabolismo , Adulto , Animales , Antioxidantes/metabolismo , Encéfalo/citología , Células COS , Línea Celular Tumoral , Chlorocebus aethiops , Epéndimo/química , Regulación de la Expresión Génica/fisiología , Humanos , Sueros Inmunes/metabolismo , Inmunohistoquímica , Recién Nacido , Ratones , Neuronas/química , Proteoma/química , Selenio/sangre , Selenio/fisiología , Selenoproteína P/inmunologíaRESUMEN
Scanning the hypothalamus of rats for receptor binding sites of the octapeptide hormone angiotensin II (ANG II), we observed ANG II-sensitive fibres in the ventrolateral hypothalamus. The ANG II (AT(1))-receptor-immunoreactive processes originate from cells-probably tanycytes-embedded in the base and the ventrolateral walls of the third ventricle and reach into the retrochiasmatic area, the ventrolateral hypothalamus and the median eminence.
Asunto(s)
Epéndimo/química , Hipotálamo/química , Fibras Nerviosas/química , Receptores de Angiotensina/análisis , Tercer Ventrículo/química , Angiotensina II/análisis , Animales , Inmunoquímica , Masculino , Ratas , Ratas Sprague-Dawley , Receptor de Angiotensina Tipo 1RESUMEN
CRF and urocortin, administrated systemically, exert peripheral biological actions which may be mediated by brain pathways. We identified brain neuronal activation induced by intravenous (i.v.) injection of CRF and urocortin in conscious rats by monitoring Fos expression 60 min later. Both peptides (850 pmol/kg, i.v.) increased the number of Fos immunoreactive cells in the paraventricular nucleus of the hypothalamus, supraoptic nucleus, central amygdala, nucleus tractus solitarius and area postrema compared with vehicle injection. Urocortin induced a 4-fold increase in the number of Fos-positive cells in the supraoptic nucleus and a 3.4-fold increase in the lateral magnocellular part of the paraventricular nucleus compared with CRF. Urocortin also elicited Fos expression in the accessory hypothalamic neurosecretory nuclei, ependyma lining the ventricles and choroid plexus which was not observed after CRF. The intensity and pattern of the Fos response were dose-related (85, 255 and 850 pmol/kg, i.v.) and urocortin was more potent than CRF. Neither CRF nor urocortin induced Fos expression in the lateral septal nucleus, Edinger-Westphal nucleus, dorsal raphe nucleus, locus coeruleus, or hypoglossal nucleus. These results show that urocortin, and less potently CRF, injected into the circulation at picomolar doses activate selective brain nuclei involved in the modulation of autonomic/endocrine function; in addition, urocortin induces a distinct activation of hypothalamic neuroendocrine neurons.
Asunto(s)
Hormona Liberadora de Corticotropina/farmacología , Hipotálamo/metabolismo , Sistemas Neurosecretores/metabolismo , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Amígdala del Cerebelo/química , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/metabolismo , Animales , Anticuerpos , Plexo Coroideo/química , Plexo Coroideo/efectos de los fármacos , Plexo Coroideo/metabolismo , Epéndimo/química , Epéndimo/efectos de los fármacos , Epéndimo/metabolismo , Nervio Hipogloso/química , Nervio Hipogloso/efectos de los fármacos , Nervio Hipogloso/metabolismo , Área Hipotalámica Lateral/química , Área Hipotalámica Lateral/efectos de los fármacos , Área Hipotalámica Lateral/metabolismo , Hipotálamo/química , Hipotálamo/efectos de los fármacos , Inmunohistoquímica , Inyecciones Intravenosas , Locus Coeruleus/química , Locus Coeruleus/efectos de los fármacos , Locus Coeruleus/metabolismo , Masculino , Mesencéfalo/química , Mesencéfalo/efectos de los fármacos , Mesencéfalo/metabolismo , Sistemas Neurosecretores/química , Sistemas Neurosecretores/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/química , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Proteínas Proto-Oncogénicas c-fos/análisis , Proteínas Proto-Oncogénicas c-fos/inmunología , Núcleos del Rafe/química , Núcleos del Rafe/efectos de los fármacos , Núcleos del Rafe/metabolismo , Ratas , Ratas Sprague-Dawley , Núcleo Solitario/química , Núcleo Solitario/efectos de los fármacos , Núcleo Solitario/metabolismo , Núcleo Supraóptico/química , Núcleo Supraóptico/efectos de los fármacos , Núcleo Supraóptico/metabolismo , Urocortinas , Nervio Vago/química , Nervio Vago/efectos de los fármacos , Nervio Vago/metabolismoRESUMEN
In this study, we analyzed immunohistochemically the distribution of the A subtype of alpha 2-adrenergic receptor (alpha 2A-AR) in the rat central nervous system using light level immunohistochemistry. By using affinity-purified antisera, we found perikaryal labeling was diffuse and/or punctate; immunoreactive puncta were heterogeneous in size and number in a region-specific manner. Dense deposits of immunoreaction product were found associated with neuropil also, particularly in the lateral parabrachial nucleus, locus coeruleus, lateral septum, diagonal band, stratum lacunosum-moleculare of CA1, and various nuclei of the amygdala and extended amygdala. Prominently immunoreactive olfactory structures include the anterior olfactory nucleus and the granular layer of the olfactory bulb. The cortex was generally light to moderately labeled with greater immunoreactivity in the cingulate and insular cortices. alpha 2A-AR-like immunoreactivity was intense in the basal forebrain and continuous from the nucleus accumbens through the substantia innominata and fundus of the striatum. Most immunoreactivity in the diencephalon was restricted to the hypothalamus with light to moderate labeling in the thalamus. Generally light immunoreactivity was observed in midbrain structures. In the pons and medulla, both perikaryal and neuropil labeling were observed. Together with the accompanying paper describing the neural distribution of alpha 2C-AR-like immunoreactivity, our results provide an extensive immunohistochemical cartography of alpha 2-ARs in the adult rat central nervous system.
Asunto(s)
Sistema Nervioso Central/química , Receptores Adrenérgicos alfa 2/análisis , Animales , Ganglios Basales/química , Cerebelo/química , Corteza Cerebral/química , Epéndimo/química , Inmunohistoquímica , Sistema Límbico/química , Masculino , Bulbo Raquídeo/química , Mesencéfalo/química , Puente/química , Ratas , Ratas Sprague-Dawley , Tálamo/químicaRESUMEN
An endogenous peptide, named diazepam-binding inhibitor (DBI) capable of displacing benzodiazepines from binding sites has been recently fully characterized. In order to clearly identify the cell types responsible for the biosynthesis of DBI in the rat central nervous system, we have performed high resolution in situ hybridization in the area postrema, hypothalamus and cerebellum, using a [35S]-labeled single stranded RNA probe. Hybridization signal was detected in both semithin and ultrathin sections. In all the brain areas examined, specific labeling was exclusively observed in non-neuronal cells including ependymal and subependymal cells bordering the third ventricle. The results obtained clearly establish that DBI is synthesized by non-neuronal cells in the rat brain.